My modpoll script supports only a single inverter.
To get the data of 2 inverters, you have to create a 2nd instance of this programm (e.g. modpoll2) and modify the filenames, that get written in the ramdisk (e.v.ACVL1.txt => I2_ACVL1.txt).
The scripts in the 123solar/scripts/protocol directory have to be cloned and adjusted too (to read the data from the right files from the ramdisk).
I guess this should be a easy and quick solution to get it working.